| 11:23:10 PM PDT - Tue, Aug 7th 2018 |
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Just officially released GAMESS 2018 R2 source code, which requires compilation, has implemented ROHF active-space triples, which perhaps could be full CCSDT, and complementary CC(t,3) for CCSDt, both of which, together with previously programmed ROHF CR-CC(2,3), are powerful and relatively economic, when compared with CCSDT, tools to reproduce the correlations in ground state biradicals and bond breaking situations. Of course the above three accurate ground state calculations can be carried out for an RHF reference. CC(t,3) and CR-CC(2,3) have several variants from the crudest to the full considerations of the triple perturbative denominators, and various results can be obtained during one run, respectively, from which one can choose as needed. Actually. CC(t,3) energies can only be obtained following a CCSDt calculation in GAMESS.
Professor Piecuch's group from Michigan State University contributes to these new coupled cluster methods, evaluated and assembled into GAMESS by Professor Gordon's group.
MRCC methods in NWCHEM are also powerful implements for this area.
Remarkably and impressevely, in NWCHEM, there have been the parallel implements of RHF, ROHF and UHF full CCSDT and CCSDTQ, wonderfully benchmarkble, and active-space CCSDt, having several variants, too.
I will try the compilation.
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